Pipe "bad address" on pipe open

So, im trying to start a webserver that uses pipes to comunicate between process.

I was thinking to make a struct named ctx to send other info also.

My code looks like this:

webserver.h

typedef struct
{
    int pipefd[2];
} ctx_t;

webserver.c

int main(int argc, char *argv[]){
    ctx_t *ctx = {0};
    if(pipe(ctx->pipefd) == -1){
        perror("ctx pipe error");
        exit(EXIT_FAILURE);
    }
    ...
    ...
}

Output: "ctx pipe error: Bad address"

if instead i declare my program like this, i have no error and the programs continue

webserver.h

int pipefd[2];

webserver.c

int main(int argc, char *argv[]){
    if(pipe(pipefd) == -1){
        perror("ctx pipe error");
        exit(EXIT_FAILURE);
    }
    ...
    ...
}

Any ideas why i cant open the pipe inside a struct? I still havn't made any forks in the main program.

Thanks.

Solution

You're passing a null pointer to a function (system call) pipe() that doesn't accept null pointers. Don't do that!

ctx_t *ctx = {0};

That sets ctx to a null pointer, albeit somewhat verbosely (the braces are not necessary, though they're not harmful). You need to allocate the ctx_t structure somewhere before trying to use it.

Use:

cts_t ctx = { { 0, 0 } };

and:

if (pipe(ctx.pipefd) != 0)
    …report error etc…

Using == -1 is also OK.